This invention relates to a reversible power transmission suitable for transmitting power between a plurality of fluid actuators and a plurality of fluid power units, and more specifically to an energy converting device for transmitting or receiving fluid energy or rotary mechanical energy.
When used for positive displacement pumping this invention provides for minimal pulsation of the fluid when compared to present state of the art pumps which are limited by the mechanical geometry of their crank mechanism.
Present positive displacement pumps are usually reciprocating piston or plunger pumps, wherein pistons slide back and forth within cylinders or plungers slide back and forth within stuffing boxes to decrease and increase the working volume. Check valves control the entry into and the discharge from the working volume to create a flow by the alternating suction and discharge action of the piston and plunger.
To provide for a smoothing of the pulsating discharge flow, two working volumes are often located opposite one another with a common piston between to produce a double acting pump. The pulsating discharge flow may be further smoothed by adding short-time accumulators in the pipelines to dampen the peaks and fill in the valleys. Alternately, it is common practice to utilize several in-line cylinders operated by a common drive, each piston located at a different displaced position within its cylinder so that overlapping of the discharge strokes may smooth the total discharge flow.
Such positive displacement pumps have many uses and are specially suited for pumping fluids at high volumes, and pressures. Typical of such utilization would be in the pipeline transportation of oil, gas, or heavy slurries such as coal, iron ore, or limestone for example. Other typical uses would be for dredging sand, gravel, silt, and clay, pumping water, and compressing gases.
The advantages of the piston or plunger positive displacement pump include a good self-priming capability and relatively high energy efficiency, however, this efficiency could be improved by the elimination of the pulsating delivery flow. While the arrangements described above do smooth the delivery rate significantly, there still remains a degree of pulsation. Heavy fluids, such as drilling mud, represent considerable momentum once a column is put in motion, and the pulsating delivery of such a massive column results in an energy loss, whereas a constant flow rate would take advantage of the momentum of this moving column to yield an improvement in efficiency as well as reduce the fatigue on pipelines which must absorb this pulsed energy. Other disadvantages of present pumps, particularly those of the large variety, include large space requirements at the pump site, and heavy weight with its associated support structure requirements.